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The Meramec River and the Lower Missouri River are the two most important forested watersheds in the Midwest for drinking water, according to two studies conducted by the Missouri Department of Conservation and the U.S.D.A. Forest Service.

The land along the edge of a river or stream is called the riparian zone. Forests are especially important in the riparian zone for preserving water quality. They stabilize the banks, filter out pesticides, nutrients, and sediments before they can reach the stream, and shade the stream, maintaining water temperatures conducive to healthy aquatic ecosystems.

Missouri has 3,238,536 acres of potential riparian forest buffer, of which 1,782,368 (55%) are currently forested. According to the Missouri Department of Natural Resources, soil is the single largest pollutant in Missouri’s water (by amount). The rate of soil erosion in Missouri is 5.3 tons per acre per year, and over 5 million acres have soil erosion above acceptable levels.

The forested watersheds with the highest ability to provide clean drinking water are the Current River and Upper St. Francis (scoring 8 out of a possible 10). However, the Current is not used as a source of drinking water, and the Upper St. Francis provides drinking water to only 6,541 people. The Meramec and Lower Missouri Rivers provide drinking water to more than 1 million people. The Meramec scores 6 out of 10, while the Lower Missouri scores 5 out of 10 respectively. (See map at right.)

(Click on map for larger view.)

Three other forested watersheds in Missouri made the list of the most important 20 midwestern streams for drinking water: the Cahokia-Joachim Watershed provides drinking water for 218,742 customers, and was rated 5 out of 10 in its ability to provide clean water; the North Fork-White Watershed provides water for 15,458 customers and was rated 7 out of 10; and the Big river provides water for 16,000 customers, and was rated 7 out of 10.

Near Kansas City, the “Missouri River – Crooked” section of the river supplies drinking water to 507,247 customers, and is ranked 2 out of 10 in its ability to supply clean drinking water. This watershed is much less forested than the ones discussed above.

Now, as reported in previous posts, direct assessments of the quality of Missouri’s drinking water find that it is high. But the data here suggest that maintaining the quality of the riparian border is one of the challenges facing Missouri’s forests.